U.S. patent application number 15/817969 was filed with the patent office on 2018-05-31 for electrode and method for making an electrode.
The applicant listed for this patent is SAINT-GOBAIN PERFORMANCE PLASTICS CORPORATION. Invention is credited to Antoine DIGUET, Romain HIVET.
Application Number | 20180149610 15/817969 |
Document ID | / |
Family ID | 62190765 |
Filed Date | 2018-05-31 |
United States Patent
Application |
20180149610 |
Kind Code |
A1 |
DIGUET; Antoine ; et
al. |
May 31, 2018 |
ELECTRODE AND METHOD FOR MAKING AN ELECTRODE
Abstract
An electrode may include a substrate, a first layer and a second
layer. The first layer may include an inorganic material. The first
layer may further be disposed between the substrate and the second
layer. The second layer may include ruthenium. The second layer may
further have a hexagonal compact crystalline structure.
Inventors: |
DIGUET; Antoine; (Paris,
FR) ; HIVET; Romain; (Saint-Ouen, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAINT-GOBAIN PERFORMANCE PLASTICS CORPORATION |
Solon |
OH |
US |
|
|
Family ID: |
62190765 |
Appl. No.: |
15/817969 |
Filed: |
November 20, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62428143 |
Nov 30, 2016 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 27/3271 20130101;
G01N 27/36 20130101 |
International
Class: |
G01N 27/327 20060101
G01N027/327; G01N 27/36 20060101 G01N027/36 |
Claims
1. An electrode comprising: a substrate; a first layer comprising
an inorganic material; and a second layer comprising ruthenium,
wherein the second layer has a hexagonal compact crystalline
structure, and wherein the first layer is disposed between the
substrate and the second layer.
2. An electrode comprising: a substrate; a first layer comprising
an inorganic material; and a second layer comprising ruthenium,
wherein the first layer is disposed between the substrate and the
second layer, and wherein the second layer has a Crystal
Orientation Ratio of at least about 20.
3. The electrode of claim 2, wherein the second layer has a sheet
resistance of at least about 2.0 Ohm/sq.
4. The electrode of claim 2, wherein the inorganic material
comprises a crystalline material or a polycrystalline material.
5. The electrode of claim 2, wherein the inorganic material
comprises an oxide, a metal oxide, a transparent oxide, a
transparent metal oxide, a dielectric compound and any combination
thereof.
6. The electrode of claim 2, wherein the inorganic material
comprises zinc oxide, indium oxide, tin oxide, cadmium oxide and
any combination thereof.
7. The electrode of claim 2, wherein the inorganic material
comprises aluminum zinc oxide (AZO), indium tin oxide (ITO),
antimony tin oxide (ATO), fluorine tin oxide (FTO) and any
combination thereof.
8. The electrode of claim 2, wherein the inorganic material
comprises aluminum zinc oxide (AZO).
9. The electrode of claim 2, wherein the inorganic material of the
first layer has a shorter lattice parameter a.sub.1 and the metal
of the second layer has a shorter lattice parameter a.sub.2, where
a.sub.1 and a.sub.2 satisfy the following formula:
*(a.sub.1/a.sub.2)=x, where x represents a value of at least about
0.98 and not greater than about 1.02.
10. The electrode of claim 2, wherein the first layer does not
contain tin oxide.
11. The electrode of claim 2, wherein the first layer does not
contain carbon.
12. The electrode of claim 2, wherein the first layer has a
thickness of not greater than about 20 nm and at least about 1
nm.
13. The electrode of claim 2, wherein the metal of the second layer
(or the layer comprising a metal) comprises a crystalline material
and a polycrystalline material.
14. The electrode of claim 2, wherein the second layer has a
thickness of at least about 10 nm and not greater than about 150
nm.
15. An electrode comprising: a substrate; and a first layer
comprising an inorganic material having a shorter lattice parameter
a.sub.1; and a second layer comprising a ruthenium having a shorter
lattice parameter a.sub.2, wherein a.sub.1 and a.sub.2 satisfy the
following formula: *(a.sub.1/a.sub.2)=x, where x represents a value
of at least about 0.98 and not greater than about 1.02.
16. The electrode of claim 15, wherein the second layer has a sheet
resistance of at least about 2.0 Ohm/sq.
17. The electrode of claim 15, wherein the inorganic material
comprises a crystalline material or a polycrystalline material.
18. The electrode of claim 15, wherein the inorganic material
comprises an oxide, a metal oxide, a transparent oxide, a
transparent metal oxide, a dielectric compound and any combination
thereof.
19. The electrode of claim 15, wherein the inorganic material
comprises zinc oxide, indium oxide, tin oxide, cadmium oxide and
any combination thereof.
20. The electrode of claim 15, wherein the inorganic material
comprises aluminum zinc oxide (AZO), indium tin oxide (ITO),
antimony tin oxide (ATO), fluorine tin oxide (FTO) and any
combination thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This Application claims priority under 35 U.S.C. .sctn.
119(e) to U.S. Provisional Patent Application No. 62/428,143,
entitled "ELECTRODE AND METHOD FOR MAKING AN ELECTRODE," by Antoine
DIGUET et al., filed Nov. 30, 2016, which is assigned to the
current assignee hereof and is incorporated herein by reference in
its entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to an electrode, and more
particularly to, a thin film electrode for biosensor
applications.
RELATED ART
[0003] Electrochemical glucose biosensors generally include two
electrodes with at least one of the electrodes having both a
metallic layer and a non-metallic layer in direct contact with the
metallic layer. The reactivity of certain noble metal electrodes
that may be included in an electrochemical glucose biosensor is
generally more pronounced immediately after production, but may be
reduced and sometimes eliminated in significantly aged products.
The non-metallic layer is generally a carbon layer that is used to
create an activated electrode that, when new, mimics the
characteristics of a non-activated product that has not been aged.
In other words, the sensitivity of the electrode is sacrificed for
a consistent reading of potential.
[0004] However, there is a continuing need for an electrode with
improved performance. For example, reducing the amount of metal,
particularly expensive metals such as gold, used in the electrode
can reduce cost. Further, there remains a need for an electrode
with a reduced amount of metal that can maintain performance.
SUMMARY
[0005] According to one aspect, an electrode may include a
substrate, a first layer and a second layer. The first layer may
include an inorganic material. The first layer may further be
disposed between the substrate and the second layer. The second
layer may include ruthenium. The second layer may further have a
hexagonal compact crystalline structure.
[0006] According to yet another aspect, an electrode may include a
substrate, a first layer and a second layer. The first layer may
include an inorganic material. The first layer may further be
disposed between the substrate and the second layer. The second
layer may include ruthenium. The second layer may further have a
Crystal Orientation Ratio (COR) of at least about 20.
[0007] According to still another aspect, an electrode may include
a substrate, a first layer and a second layer. The first layer may
include an inorganic material. The first layer may further be
disposed between the substrate and the second layer. The second
layer may include ruthenium. The first layer may have a shorter
lattice parameter a.sub.1 and the second layer may have a shorter
lattice parameter a.sub.2, such that a.sub.1 and a.sub.2 satisfy
the following formula: *(a.sub.1/a.sub.2)=x, where x represents a
value of at least about 0.98 and not greater than about 1.02.
[0008] According to yet another aspect, a biosensor test strip may
include an electrode system that includes an electrode. The
electrode may include a substrate, a first layer and a second
layer. The first layer may include an inorganic material. The first
layer may further be disposed between the substrate and the second
layer. The second layer may include ruthenium. The second layer may
further have a hexagonal compact crystalline structure.
[0009] According to still another aspect, a method of forming an
electrode may include providing a substrate, depositing a first
layer on the substrate, and depositing a second layer on the first
layer. The first layer may further be disposed between the
substrate and the second layer. The second layer may include
ruthenium. The second layer may further have a hexagonal compact
crystalline structure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Embodiments are illustrated by way of example and are not
limited by the accompanying figure.
[0011] FIG. 1 includes an illustration of an electrode according to
embodiments described herein;
[0012] FIG. 2a includes a chart comparing the X-ray diffraction
plots for an electrode according to embodiments described herein
and a comparative electrode; and
[0013] FIG. 2b includes a chart comparing the X-ray diffraction
plots for an electrode according to embodiments described herein
and a comparative electrode.
[0014] Skilled artisans appreciate that elements in the figures are
illustrated for simplicity and clarity and have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements in the figures can be exaggerated relative to other
elements to help to improve understanding of embodiments of the
invention.
DETAILED DESCRIPTION
[0015] The following description in combination with the figures is
provided to assist in understanding the teachings disclosed herein.
The following discussion will focus on specific implementations and
embodiments of the teachings. This focus is provided to assist in
describing the teachings and should not be interpreted as a
limitation on the scope or applicability of the teachings. However,
other embodiments can be used based on the teachings as disclosed
in this application.
[0016] The terms "comprises," "comprising," "includes,"
"including," "has," "having" or any other variation thereof, are
intended to cover a non-exclusive inclusion. For example, a method,
article, or apparatus that comprises a list of features is not
necessarily limited only to those features but can include other
features not expressly listed or inherent to such method, article,
or apparatus. Further, unless expressly stated to the contrary,
"or" refers to an inclusive-or and not to an exclusive-or. For
example, a condition A or B is satisfied by any one of the
following: A is true (or present) and B is false (or not present),
A is false (or not present) and B is true (or present), and both A
and B are true (or present).
[0017] Also, the use of "a" or "an" is employed to describe
elements and components described herein. This is done merely for
convenience and to give a general sense of the scope of the
invention. This description should be read to include one, at least
one, or the singular as also including the plural, or vice versa,
unless it is clear that it is meant otherwise. For example, when a
single item is described herein, more than one item can be used in
place of a single item. Similarly, where more than one item is
described herein, a single item can be substituted for that more
than one item.
[0018] Unless otherwise defined, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. The
materials, methods, and examples are illustrative only and not
intended to be limiting. To the extent not described herein, many
details regarding specific materials and processing acts are
conventional and can be found in textbooks and other sources within
the electrode and biosensor arts.
[0019] Embodiments described herein are generally directed to an
electrode or a method of forming an electrode where the electrode
includes a substrate, a first layer, and a second layer. The first
layer may include an inorganic material and the second layer may
include ruthenium. According to particular embodiments, the second
layer may have a hexagonal compact crystalline structure. According
to still other embodiments, the second layer may have a Crystal
Orientation Ratio (COR) of at least about 20. According to yet
other embodiments, the first layer may have a shorter lattice
parameter a.sub.1 and the second layer may have a shorter lattice
parameter a.sub.2, such that a.sub.1 and a.sub.2 satisfy the
following formula: *(a.sub.1/a.sub.2)=x, where x represents a value
of at least about 0.98 and not greater than about 1.02.
[0020] In certain embodiments, an electrode formed according to
embodiments described herein can be a thin film electrode.
According to still other embodiment, the thin film electrode can be
for us in biosensors or biosensor test strips that measure the
glucose level in a sample, such as, a blood sample.
[0021] According to still other embodiments described herein, a
biosensor or biosensor test strip may include an electrode formed
according to embodiments described herein. For example, a biosensor
or biosensor test strip may include an electrode that may include a
substrate, a first layer and a second layer. The first layer may
include an inorganic material and the second layer may include
ruthenium. According to particular embodiments, the second layer
may have a hexagonal compact crystalline structure. According to
still other embodiments, the second layer may have a Crystal
Orientation Ratio (COR) of at least about 20. According to yet
other embodiments, the first layer may have a shorter lattice
parameter a.sub.1 and the second layer may have a shorter lattice
parameter a.sub.2, such that a.sub.1 and a.sub.2 satisfy the
following formula: *(a.sub.1/a.sub.2)=x, where x represents a value
of at least about 0.98 and not greater than about 1.02.
[0022] FIG. 1 includes an illustration showing the configuration of
an electrode 10 formed according to embodiments described herein.
As shown in FIG. 1, electrode 10 may include a substrate 20, a
first layer 30 and a second layer 40. As illustrated, the first
layer 30 can be disposed adjacent to the substrate 20 and the
second layer 40 can be disposed adjacent to the first layer 30 such
that the first layer 30 is located between the substrate 20 and the
second layer 40.
[0023] According to certain embodiments, the first layer 30 can
directly contact the substrate 20, the second layer 40, or both.
For example, the first layer 30 can be disposed directly adjacent
the substrate 20 such that the first layer 30 is directly
contacting the substrate 20. Additionally, the second layer 40 can
be disposed directly adjacent the first layer 30 such that the
second layer 40 is directly contacting the first layer 30.
[0024] According to still other embodiments, the electrode 10 can
include additional layers. For example, the electrode 10 can
include an intermediate layer or intermediate layers (not show in
FIG. 1) disposed between one or more of the substrate 20, the first
layer 30, and the second layer 40.
[0025] According to yet other embodiments, the electrode 10 formed
as described herein may be an inert electrode, such as, an inert
thin film electrode.
[0026] In certain embodiments, the electrode 10 can be a biosensor
electrode, such as, for example, a biosensor electrode that can
measure the glucose level of a sample, such as, a blood sample. In
particular embodiments, the electrode 10 can contain a layer
comprising a chemical solution (not shown in FIG. 1), such as a
solution containing an enzyme, a mediator, an indicator, or any
combination thereof. In particular embodiments, the electrode 10
can be reactive to glucose. For example, glucose can be indirectly
degraded by the electrode 10 by first reacting with an enzyme to
form a subproduct and the electrode 10 is reactive with the
subproduct.
[0027] According to still other embodiments, the electrode 10 can
be part of a biosensor, such as, a biosensor test strip adapted to
measure the level of glucose in a sample, such as, a blood sample.
In certain embodiments, the test strip can include a working
electrode and a counter electrode and the electrode 10 described
herein can be present as the working electrode, the counter
electrode, or both.
[0028] According to yet other embodiments, the first layer 30 and
the second layer 40 can be epitaxial layers and, particularly,
heteroepitaxial layers. In more particular embodiments, the first
layer 30 can be a growth underlayer and the second layer 40 can be
an epitaxial overlayer. Epitaxy may refer to the deposition of a
crystalline overlayer over a crystalline underlayer. Homoepitaxy
may refer to the overlayer and the underlayer being formed of the
same material. Heteroepitaxy may refer to the epitaxial overlayer
being formed on a growth underlayer of a different material. In
epitaxial growth, the underlayer can act as a seed crystal locking
the overlayer into one or more ordered crystallographic
orientations with respect to the underlayer. Growth can be
non-epitaxial if the overlayer does not form an ordered layer with
respect to the underlayer.
[0029] In certain embodiments, the introduction of a growth
underlayer can improve the quality of the electrode, such as to
improve its sheet resistance. In other words, as compared to an
electrode without the growth underlayer, it has been surprisingly
discovered that in certain embodiments, it is possible to decrease
the amount of metal in the epitaxial overlayer by about 10% while
maintaining the same sheet resistance of the electrode.
[0030] Sheet resistance measures the electrical resistance of thin
films that are nominally uniform in thickness. Commonly, electrical
resistivity is presented in units such as .OMEGA.cm. To obtain a
sheet resistance value, electrical resistivity is divided by the
sheet thickness, and the unit can be represented as .OMEGA.. To
avoid being misinterpreted as bulk resistance of 1 ohm, an
alternate common unit for sheet resistance is "ohms per square"
(denoted ".OMEGA./sq" or ".OMEGA./.quadrature."), which is
dimensionally equal to an ohm, but is exclusively used for sheet
resistance.
[0031] While the sheet resistance is a measure of the whole
electrode, the contribution of the substrate and the first layer
are negligible. For example, in one embodiment, the substrate can
provide no contribution to the sheet resistance of the electrode.
In further embodiments, the contribution of a 5 nm AZO underlayer
to the total measured sheet resistance of the electrode is
negligible, such as about 0.0005 Ohm/sq.
[0032] According to particular embodiments, the electrode 10 can
have a particular sheet resistance. For example, the electrode 10
may have a sheet resistance of at least about 2.0 Ohms/sq, such as,
at least about 2.25 Ohms/sq, at least about 2.5 Ohms/sq, at least
about 2.75 Ohms/sq, at least about 3.0 Ohms/sq, at least about 4.0
Ohms/sq, at least about 5.0 Ohms/sq or even at least about 10
Ohms/sq.
[0033] According to certain embodiments, the substrate 20 may be
constructed out of any material suitable for the substrate of an
electrode. According to certain embodiments, the material forming
the substrate can contain a polymer, a flexible polymer, or a
transparent polymer. Suitable polymers can include, for example,
polycarbonate, polyacrylate, polyester, polyethylene terephthalate
(PET), polyethylene naphthalate (PEN), cellulose triacetated (TCA
or TAC), polyurethane, or any combination thereof. In particular
embodiments, the substrate can be a glass substrate, such as a
transparent glass substrate.
[0034] According to yet other embodiments, the substrate 20 may
have a particular thickness suitable for an electrode. For example,
the substrate 20 may have a thickness of at least about 1 micron,
such as, at least about 5 microns, at least about 10 microns, at
least about 15 microns, at least about 20 microns, at least about
25 microns, at least about 30 microns, at least about 35 microns,
at least about 40 microns, at least about 45 microns or even at
least about 50 microns. According to still other embodiments, the
substrate 20 may have a thickness of not greater than about 1,000
microns, such as, not greater than about 750 microns, not greater
than about 500 microns, not greater than about 400 microns or even
not greater than about 300 microns. It will be appreciated that the
substrate 20 may have a thickness within a range between any of the
minimum and maximum values noted above. It will be further
appreciated that the substrate 20 may have a thickness of any value
between any of the minimum and maximum values noted above. For
example, the substrate can have a thickness in a range of from
about 20 microns to about 500 microns or from about 40 microns to
about 300 microns. In very particular embodiments, the substrate
can have a thickness in a range of from about 100 microns to about
300 microns.
[0035] According to still other embodiments and as shown in FIG. 1,
a surface 22 of the substrate 20 that is adjacent to first layer 30
can be mechanically treated to improve adhesion between the
substrate 20 and first layer 30. For example, mechanically treating
the surface 22 of the substrate 20 can include blasting or
mechanically etching the surface 22 of the substrate 20.
[0036] According to yet other embodiments, the surface 22 of the
substrate 20 may have a particular surface roughness (R.sub.rms).
For example, the surface 22 may have a roughness of at least about
1 nm, such as, at least about 2 nm, at least about 3 nm, at least
about 4 nm, at least about 5 nm, at least about 10 nm, at least
about 50 nm or even at least about 100 nm. According to yet other
embodiments, the surface 22 may have a surface roughness of not
greater than about 200 nm, such as, not greater than about 180 nm,
not greater than about 160 nm, not greater than about 140 nm or
even not greater than about 120 nm. It will be appreciated that the
surface 22 may have a surface roughness of any value within a range
between any of the minimum and maximum values noted above. It will
be further appreciated that the surface 22 may have a thickness of
any value between any of the minimum and maximum values noted
above.
[0037] Referring again to FIG. 1, first layer 30 may be disposed
over substrate 20. For example, first layer 30 may be disposed
between substrate 20 and second layer 40.
[0038] According to particular embodiments, the first layer 30 may
contain one or more of the following materials and the one or more
materials contained in the first layer can have one or more, or
even all, of the following characteristics.
[0039] According to certain embodiments, the first layer 30 may
include an inorganic material, such as, an oxide, a metal oxide, a
transparent metal oxide, a dielectric compound or a combination
thereof. According to particular embodiments, the first layer 30
may be a dielectric layer that may contain a dielectric material.
According to certain embodiments, the particular dielectric
materials may include a metal oxide. According to still other
embodiments, the metal oxide may include zinc oxide, indium oxide,
tin oxide, cadmium oxide, or any combination thereof. For example,
suitable metal oxides may be aluminum zinc oxide (AZO), indium tin
oxide (ITO), antimony tin oxide (ATO), fluorine tin oxide (FTO), or
any combination thereof. In very particular embodiments, the first
layer can contain AZO. According to still other embodiments, the
first layer may be an AZO layer.
[0040] According to certain embodiments, the first layer 30 may
include a crystalline material. According to still other
embodiments, the first layer 30 may include a polycrystalline
material.
[0041] According to yet other embodiments, the first layer 30 may
contain substantially no carbon. According to yet other embodiment,
the first layer 30 may contain substantially no carbon in the form
of graphite.
[0042] According to still other embodiments, the first layer may
include a particular content of inorganic material. For example,
the first layer may include at least about 50 wt. % inorganic
material for a total weight of the first layer, such as, at least
about 55 wt. %, at least about 60 wt. %, at least about 65 wt. %,
at least about 70 wt. %, at least about 75 wt. %, at least about 80
wt. %, at least about 85 wt. %, at least about 90 wt. %, at least
about 95 wt. % inorganic material for a total weight of the first
layer. According to still other embodiments, the first layer may
include not greater than about 100 wt. %, such as, not greater than
about 99 wt. %, not greater than about 95 wt. %, not greater than
about 90 wt. %, not greater than about 85 wt. %, not greater than
about 80 wt. %, not greater than about 75 wt. % inorganic material
for a total weight of the first layer. It will be appreciated that
the total content of inorganic material in the first layer may be
any value within a range between any of the minimum and maximum
values noted above. It will be further appreciated that the total
content of inorganic material in the first layer may be any value
between any of the minimum and maximum values noted above.
[0043] According to still other embodiments, the first layer 30 may
have a particular thickness. For example, the first layer 30 may
have a thickness of not greater than about 20 nm, such as, not
greater than about 17 nm, not greater than about 15 nm, not greater
than about 13 nm, not greater than about 10 nm, not greater than
about 7 nm or even not greater than about 5 nm. According to still
other embodiments, the first layer 30 may have a thickness of at
least about 1 nm, such as, at least about 2 nm, at least about 3
nm, at least about 4 nm or even at least about 5 nm. It will be
appreciated that the thickness of the first layer 30 may be any
value within a range between any of the minimum and maximum values
noted above. It will be further appreciated that the thickness of
the first layer 30 may be any value between any of the minimum and
maximum values noted above.
[0044] According to yet other embodiments, the first layer 30 may
consist essentially of a metal oxide. As used herein, the phrase
"consisting essentially of a metal oxide" refers to at least 95
atomic % of a metal oxide.
[0045] Referring again to FIG. 1, second layer 40 can contain one
or more of the following materials and the one or more materials
contained in the second layer can have one or more, or even all, of
the following characteristics.
[0046] According to particular embodiments and as noted herein, the
second layer 40 may include ruthenium. According to still other
embodiments the second layer may be a ruthenium layer.
[0047] According to yet other embodiments, the second layer 40 may
include a crystalline material. According to still other
embodiments, the second layer 40 may include a polycrystalline
material. According other embodiments the ruthenium of the second
layer 40 may be a crystalline material. According to yet other
embodiments, the ruthenium of the second layer 40 may be a
polycrystalline material.
[0048] According to yet other embodiments, the second layer 40 may
have a hexagonal compact crystalline structure. According to still
other embodiments, the ruthenium material of the second layer 40
may have a hexagonal compact crystalline structure.
[0049] According to certain embodiments, the second layer 40 may be
referred to as a film. According to yet other embodiment, the
second layer 40 may be referred to as a thin film.
[0050] According to certain embodiments, the second layer 40 may
have a particular thickness. For example, the second layer 40 may
have a thickness of at least about 10 nm, such as, at least about
15 nm, at least about 20 nm, at least about 25 nm, at least about
30 nm, at least about 35 nm, at least about 40 nm, at least about
45 nm or even at least about 50 nm. According to still other
embodiments, the second layer 40 may have a thickness of not
greater than about 150 nm, such as, not greater than about 140 nm,
not greater than about 130 nm, not greater than about 120 nm, not
greater than about 110 nm or even not greater than about 100 nm. It
will be appreciated that the thickness of the second layer 40 may
be any value within a range between any of the minimum and maximum
values noted above. It will be further appreciated that the
thickness of the second layer 40 in the first layer may be any
value between any of the minimum and maximum values noted
above.
[0051] According to yet other embodiments, the second layer 40 may
have a particular total thickness variation (TTV). For example, the
second layer 40 may have TTV of not greater than about 15 nm, such
as, not greater than about 10 nm, not greater than about 8 nm, not
greater than about 6 nm, not greater than about 5 nm or even not
greater than about 4 nm. As used herein, the TTV is the difference
between maximum and minimum thickness values along a square
millimeter segment spanning the length and width of the layer.
[0052] According to yet other embodiments, aspects of the electrode
may be described as having a particular performance, such as, by
having a particular Visible Light Transmittance (VLT). The VLT is a
measure of the amount the visible spectrum (380 to 780 nanometers)
that is transmitted through a composite or layer and, as described
herein, is presented as a percentage. The VLT can be measured
according to standard ISO 9050. Although ISO 9050 refers to
glazings, the same procedure can be used with a film taped or
otherwise adhered to a transparent substrate.
[0053] According to particular embodiments, the second layer 40 may
have a particular VLT. For example, the second layer 40 may have a
VLT of not greater than about 70%, such as, not greater than about
60%, not greater than about 50%, not greater than about 40%, not
greater than about 30%, not greater than about 25%, not greater
than about 20%, not greater than about 15%, not greater than about
10%, not greater than about 5%, not greater than about 4%, not
greater than about 3%, not greater than about 2%, or no greater
than 1%. According to yet other embodiments, the second layer 40
may have a VLT of at least about 1%, such as, at least about 2%, at
least about 3%, at least about 4%, at least about 5% or even at
least about 10%. It will be appreciated that the second layer 40
may have a VLT of any value within a range between any of the
minimum and maximum values noted above. It will be further
appreciated that the second layer 40 may have a VLT of any value
between any of the minimum and maximum values noted above.
[0054] According to certain embodiments, the VLT of the second
layer 40 may be related, such as inversely proportional, to the
thickness of the second layer 40. In other words, in certain
embodiments, the VLT of the second layer 40 may tend to decrease as
the thickness of the second layer 40 increases.
[0055] According to other embodiments, the second layer 40 can
contain ruthenium at a particular content. For example, the second
layer 40 may contain ruthenium in an amount of at least about 50
wt. % for a total weight of the second layer 40, such as, at least
about 60 wt. %, at least about 70 wt. %, at least about 80 wt. %,
at least about 90 wt. %, at least about 99 wt. % for a total weight
of the second layer 40. According to yet other embodiments, the
second layer 40 can contain ruthenium in an amount of not greater
than about 99 wt. % for a total weight of the second layer 40, such
as, not greater than about 95 wt. % or even not greater than about
90 wt. % for a total weight of the second layer 40. It will be
appreciated that the second layer 40 may contain ruthenium at an
amount of any value within a range between any of the minimum and
maximum values noted above. It will be further appreciated that the
second layer 40 may contain ruthenium at an amount of any value
between any of the minimum and maximum values noted above.
[0056] According to still other embodiments, the second layer 40
may contain an essentially pure metal or in other embodiments, a
metal alloy. As used herein, "essentially pure metal" refers to a
metal oxide having possible impurities in an amount of less than
about 5 atomic %.
[0057] According to other embodiments, the second layer 40 may have
a particular conductivity. For example, the second layer 40 may
have a conductivity of not greater than 15.times.10.sup.-6 Ohmcm,
such as, not greater than 13.times.10.sup.-6 Ohmcm, not greater
than 11.times.10.sup.-6 Ohmcm, not greater than 10.times.10.sup.-6
Ohmcm, not greater than 9.times.10.sup.-6 Ohmcm, not greater than
8.times.10.sup.-6 Ohmcm, not greater than 7.times.10.sup.-6 Ohmcm,
or even not greater than 6.times.10.sup.-6 Ohmcm. According to yet
other embodiments, the second layer 40 may have a conductivity of
at least about 1.times.10.sup.-6 Ohmcm, such as, at least about
2.times.10.sup.-6 Ohmcm, at least about 3.times.10.sup.-6 Ohmcm or
even at least about 4.times.10.sup.-6 Ohmcm. It will be appreciated
that the second layer 40 may have a conductivity of any value
within a range between any of the minimum and maximum values noted
above. It will be further appreciated that the second layer 40 may
have a conductivity of any value between any of the minimum and
maximum values noted above.
[0058] According to still other embodiments, the second layer 40
may have a particular Crystal Orientation Ratio (COR). For purposes
of embodiments described herein, the COR of the second layer 40 may
be calculated from X-ray diffraction (i.e., Bragg-Brentano
geometry) plot measured from the second layer and may be equal to
the ratio of the peak intensity of the plot at 42.degree. divided
by the peek intensity of the plot at 44.degree.. For example, the
second layer 40 may have a COR of not greater than about 20.
[0059] According to still other embodiments, the first layer 30 and
the second layer 40 may have a particular crystalline structure
mismatch. The crystal structure of a material or of a layer (i.e.,
the arrangement of atoms within a given type of crystal) can be
described in terms of its simplest repeating unit, referred to as a
unit cell, having unit-cell-edge lengths a, b, and c, referred to
as lattice parameters with a being shorter lattice parameter. In
this context, the crystal structure mismatch between the first
layer 30 having a shorter lattice parameter (a.sub.1) and the
second layer 40 having a shorter lattice parameter (a.sub.2) may be
defined by the following formula: *(a.sub.1/a.sub.2)=x, where x
represents a value of at least about 0.98, such as, at least about
0.99 or even at least about 1.0. According to still other
embodiments, the crystal structure mismatch between the first layer
having a shorter lattice parameter (a.sub.1) and the second layer
having a shorter lattice parameter (a.sub.2) may be defined by the
following formula: *(a.sub.1/a.sub.2)=x, where x represents a value
of not greater than about 1.02. It will be appreciated that the x
value of the formula defining crystal structure mismatch may be any
value within a range between any of the minimum and maximum values
noted above. It will be further appreciated that the x value of the
formula defining crystal structure mismatch may be any value
between any of the minimum and maximum values noted above.
[0060] For example, the crystal structure of gold is face centered
cubic (fcc) and its lattice parameter a is 0.408 nm. Because the
crystal structure of gold is cubic, it can have only one lattice
parameter. Under ambient conditions, ZnO mainly crystallizes under
wurtzite form. Lattice parameters for ZnO in wurtzite form are
a=0.325 nm and c=0.520 nm. When this form is oriented in the
so-called (002) orientation, the surface can have atom distances
similar to that of gold when the gold crystal is oriented in the so
called (111) orientation. That is,
([sqrt(2)/2].times.a.sub.Au).about.a.sub.ZnO, which corresponds to
0.29 nm-0.33 nm. The effect with AZO (=ZnO:Al) can be similar, even
when Al atoms are intercalated in the network. In very particular
embodiments, AZO and gold can be used as first and second layers,
respectively.
[0061] On the other hand, if Au is deposited on another dielectric,
such as TiOx, the heteroepitaxy effect is not effective since the
mismatch between crystal structures is high. For example, when TiOx
is deposited by magnetron sputtering without thermal treatment, the
material can be amorphous (in this case there is no specific order)
or can have a rutile crystal structure. A rutile crystal structure
has a body-centered tetragonal unit cell with a=b=0.458 nm and
c=0.295 nm. In certain embodiments, from this structure, TiOx does
not appear to have a crystal structure that closely matches the
crystal structure of an Au unit cell, regardless of orientation. In
particular embodiments, the first layer can be free of tin
oxide.
[0062] According to yet other embodiments, an electrode formed
according to embodiments described herein may further include a
third layer overlying the first and the second layer. According to
certain embodiments, the third layer may include gold (Au).
According to yet other embodiments, the third layer may be a gold
layer. According to still other embodiments, the third layer may
include palladium (Pd). According to still other embodiments, the
third layer may be a palladium layer.
[0063] Also described herein are electrochemical sensors. According
to particular embodiments, the electrochemical sensors may be
adapted to detect the presence of, and/or measure the concentration
of, an analyte by way of electrochemical oxidation and reduction
reactions within the sensor. These reactions can be transduced to
an electrical signal that can be correlated to an amount or
concentration of the analyte. In certain embodiments, the
electrochemical sensor can be a biosensor test strip.
[0064] According to still other embodiments, the test strip may
include a base substrate, a spacing layer, a covering layer, or any
combination thereof. The base substrate can include an electrode
system and the electrode system can include a set of measuring
electrodes, e.g., at least a working electrode and a counter
electrode, within a sample-receiving chamber. According to
particular embodiments, one or more of the electrodes in the
electrode system can include an electrode as described herein.
[0065] Further, in particular embodiments, the spacing layer of the
test strip can define a sample-receiving chamber extending between
the base substrate and the covering layer. The sample-receiving
chamber can be adapted such that a sample fluid can enter a chamber
and be placed in electrolytic contact with both the working
electrode and the counter electrode. Such contact can allow
electrical current to flow between the measuring electrodes to
affect the electrooxidation or electroreduction of the analyte. In
very particular embodiments, the sample fluid can be a blood
sample, such as a human blood sample, and the sensor can be adapted
to measure the glucose level in such a sample.
[0066] Moreover, a suitable reagent system can overlie at least a
portion of the electrodes or electrode pairs within the
sample-receiving chamber. The reagent system can include additives
to enhance the reagent properties or characteristics. For example,
additives can include materials to facilitate the placement of the
reagent composition onto the test strip and to improve its
adherence to the strip, or for increasing the rate of hydration of
the reagent composition by the sample fluid. Additionally, the
additives can include components selected to enhance the physical
properties of the resulting dried reagent layer, and the uptake of
a liquid test sample for analysis. In certain embodiments, the
additives can include thickeners, viscosity modulators, film
formers, stabilizers, buffers, detergents, gelling agents, fillers,
film openers, coloring agents, agents endowing thixotropy, or any
combination thereof.
[0067] In further embodiments, the covering layer can be adapted to
form a top surface of the sample-receiving chamber. Moreover, the
covering layer can be adapted to provide a hydrophilic surface to
aid in acquisition of the test sample. In particular embodiments,
the covering layer can define a vent opening that allows air to
escape from the interior of the chamber as the sample fluid enters
and moves into the sample-receiving chamber.
[0068] According to certain embodiments, an electrode as described
herein can be formed according to any appropriate method. In
general, forming the electrode includes providing a substrate as
described herein, depositing the first layer as described herein,
and depositing the second layer as described herein. For example,
the first layer can be deposited over the substrate and the second
layer can be deposited over the first layer. In certain
embodiments, the first layer can be deposited directly onto the
substrate. In still other embodiments, the second layer can be
deposited directly onto the first layer.
[0069] According to still other embodiments, the method may include
depositing one or more of the layers by physical vapor deposition,
such as sputtering or even magnetron sputtering. According to
certain embodiments, the first layer 30 may be deposited with or
without annealing. In certain embodiments, the first layer 30 may
be deposited without annealing. The materials used for forming the
first layer 30 may have a standard deposition rate.
[0070] According to yet other embodiments, the first layer 30 and
the second layer 40 may be deposited by roll-to-roll processing.
Roll-to-roll processing refers to a process of applying coatings
starting with a roll of a flexible material and re-reeling after
the process to create an output roll. In certain embodiments, the
roll-to-roll process can include depositing the first and second
layers using two cathodes, such as simultaneously using two
cathodes.
[0071] According to still other embodiments, the second layer 40
may be deposited at a particular pressure. For examples, the second
layer 40 may be deposited at a pressure of not greater than about 3
mTorr, such as, not greater than about 2.8 mTorr, not greater than
about 2.5 mTorr, not greater than about 2.3 mTorr or even not
greater than about 2.0 mTorr. According to particular embodiments,
the second layer 40 may be deposited at any pressure between any of
the values noted above.
[0072] Embodiments of the method described herein can increase the
production time and improve the TTV of the coating as described
herein. In certain embodiments, the method can increase production
time by 10% as compared to conventional methods of forming a
similar electrode without a first layer 30, particularly a
dielectric layer.
[0073] The present disclosure represents a departure from the state
of the art. In particular, it has heretofore been unknown how to
form an electrode which can provide the performance
characteristics, and particularly the combination of performance
characteristics described herein. For example, the present
disclosure illustrates various electrodes having a dielectric layer
and a layer comprising ruthenium having a particular crystalline
structure, Crystal Orientation Ratio or lattice parameter mismatch.
Such constructions as described in detail herein have unexpectedly
been found to exhibit significantly superior sheet resistance that
were heretofore impossible to achieve relative to its thickness.
The introduction of the first layer as described herein can improve
the quality of the electrode. For example, it is possible to
improve the sheet resistance, or decrease the amount of material
used for the second layer, particularly expensive metals such as
gold, and maintain the same sheet resistance, as compared to an
electrode without the first layer. The concepts are better
understood in view of the embodiments described below that
illustrate and do not limit the scope of the present invention.
[0074] Many different aspects and embodiments are possible. Some of
those aspects and embodiments are described below. After reading
this specification, skilled artisans will appreciate that those
aspects and embodiments are only illustrative and do not limit the
scope of the present invention. Embodiments can be in accordance
with any one or more of the items as listed below.
Embodiment 1
[0075] An electrode comprising: a substrate; a first layer
comprising an inorganic material; and a second layer comprising
ruthenium, wherein the second layer has a hexagonal compact
crystalline structure, and wherein the first layer is disposed
between the substrate and the second layer.
Embodiment 2
[0076] An electrode comprising: a substrate; a first layer
comprising an inorganic material; and a second layer comprising
ruthenium, wherein the first layer is disposed between the
substrate and the second layer, and wherein the second layer has a
Crystal Orientation Ratio of at least about 20.
Embodiment 3
[0077] An electrode comprising: a substrate; and a first layer
comprising an inorganic material having a shorter lattice parameter
a.sub.1; and a second layer comprising a ruthenium having a shorter
lattice parameter a.sub.2, wherein a.sub.1 and a.sub.2 satisfy the
following formula: *(a.sub.1/a.sub.2)=x, where x represents a value
of at least about 0.98 and not greater than about 1.02.
Embodiment 4
[0078] A biosensor test strip comprising: an electrode system that
includes an electrode, the electrode comprising: a substrate; a
first layer comprising an inorganic material; and a second layer
comprising ruthenium, wherein the second layer has a hexagonal
compact crystalline structure, and wherein the first layer is
disposed between the substrate and the second layer.
Embodiment 5
[0079] A method of forming an electrode, the method comprising:
providing a substrate; depositing a first layer on the substrate,
wherein the first layer comprises an inorganic material; and
depositing a second layer on the first layer, wherein the second
layer comprises ruthenium, wherein the second layer has a hexagonal
compact crystalline structure, and wherein the first layer is
disposed between the substrate and the second layer.
Embodiment 6
[0080] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer has a
sheet resistance of at least about 2.0 Ohm/sq.
Embodiment 7
[0081] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the inorganic material
comprises a crystalline material or a polycrystalline material.
Embodiment 8
[0082] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the inorganic material
comprises an oxide, a metal oxide, a transparent oxide, a
transparent metal oxide, a dielectric compound and any combination
thereof.
Embodiment 9
[0083] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the inorganic material
comprises zinc oxide, indium oxide, tin oxide, cadmium oxide and
any combination thereof.
Embodiment 10
[0084] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the inorganic material
comprises aluminum zinc oxide (AZO), indium tin oxide (ITO),
antimony tin oxide (ATO), fluorine tin oxide (FTO) and any
combination thereof.
Embodiment 11
[0085] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the inorganic material
comprises aluminum zinc oxide (AZO).
Embodiment 12
[0086] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 4 and 5, wherein the inorganic material of
the first layer has a shorter lattice parameter a.sub.1 and the
metal of the second layer has a shorter lattice parameter a.sub.2,
where a.sub.1 and a.sub.2 satisfy the following formula:
*(a.sub.1/a.sub.2)=x, where x represents a value of at least about
0.98 and not greater than about 1.02.
Embodiment 13
[0087] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the first layer does
not contain tin oxide.
Embodiment 14
[0088] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the first layer does
not contain carbon.
Embodiment 15
[0089] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the first layer
comprises the inorganic material in an amount of 100% by weight of
the first layer, not greater than about 99%, not greater than about
95%, not greater than about 90%, not greater than about 85%, not
greater than about 80% and not greater than about 75%.
Embodiment 16
[0090] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the first layer
comprises the inorganic material in an amount of at least about 50%
by weight of the first layer, at least about 55%, at least about
60%, at least about 65%, at least about 70%, at least about 75%, at
least about 80%, at least about 85%, at least about 90% and at
least about 95%.
Embodiment 17
[0091] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the first layer has a
thickness of not greater than about 20 nm, not greater than about
17 nm, not greater than about 15 nm, not greater than about 13 nm,
not greater than about 10 nm, not greater than about 7 nm and not
greater than about 5 nm.
Embodiment 18
[0092] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the first layer has a
thickness of at least about 1 nm, at least about 2 nm, at least
about 3 nm, at least about 4 nm and at least about 5 nm.
Embodiment 19
[0093] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the metal of the
second layer (or the layer comprising a metal) comprises a
crystalline material and a polycrystalline material.
Embodiment 20
[0094] The electrode, biosensor test strip, composite and method of
any of embodiments 2, 3 and 4, wherein the metal of the second
layer has a hexagonal compact crystalline structure.
Embodiment 21
[0095] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer (or
the layer comprising a metal) has a visible light transmittance of
not greater than about 70%, not greater 60%, not greater than about
50%, not greater than about 40%, not greater than about 30%, not
greater than about 25%, not greater than about 20%, not greater
than about 15%, not greater than about 10%, not greater than about
5%, not greater than about 4%, not greater than about 3%, not
greater than about 2% and not greater than about 1%.
Embodiment 22
[0096] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer (or
the layer comprising a metal) has a visible light transmittance of
at least about 10%, at least about 5%, at least about 4%, at least
about 3%, at least about 2% and at least about 1%.
Embodiment 23
[0097] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer is a
film or a thin film.
Embodiment 24
[0098] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the metal of the
second layer has a purity of from 60% to 100%, from 65% to 95%,
from 70% to 90% and from 75% to 85%.
Embodiment 25
[0099] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the electrode has a
sheet resistance of at least about 2.0 Ohm/sq.
Embodiment 26
[0100] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer has a
thickness of at least about 10 nm, at least about 15 nm, at least
about 20 nm, at least about 25 nm, at least about 30 nm, at least
about 35 nm, at least about 40 nm, at least about 45 nm and at
least about 50 nm.
Embodiment 27
[0101] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer has a
thickness of not greater than about 150 nm, not greater than about
140 nm, not greater than about 130 nm, not greater than about 120
nm, not greater than about 110 nm and not greater than about 100
nm.
Embodiment 28
[0102] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer has a
thickness of from 10 nm to 150 nm, from 20 nm to 70 nm, from 30 nm
to 60 nm, from 40 nm to 50 nm and from 35 nm to 45 nm.
Embodiment 29
[0103] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer has a
resistivity of not greater than about 25.times.10.sup.-6 Ohmcm, not
greater than about 24.times.10.sup.-6 Ohmcm, not greater than about
23.times.10.sup.-6 Ohmcm and not greater than about
22.times.10.sup.-6 Ohmcm and not greater than about
21.times.10.sup.-6 Ohmcm.
Embodiment 30
[0104] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the second layer has a
resistivity of at least about 15.times.10.sup.-6 Ohmcm, at least
about 16.times.10.sup.-6 Ohmcm, at least about 17.times.10.sup.-6
Ohmcm and at least about 18.times.10.sup.-6 Ohmcm.
Embodiment 31
[0105] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the substrate
comprises a polymer, a flexible polymer and a transparent
polymer.
Embodiment 32
[0106] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the substrate
comprises polycarbonate, polyacrylate, polyester, polyethylene
terephthalate (PET), polyethylene naphthalate (PEN), cellulose
triacetated (TCA or TAC), polyurethane and any combination
thereof.
Embodiment 33
[0107] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the substrate
comprises polyethylene terephthalate (PET).
Embodiment 34
[0108] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the substrate has a
thickness of at least about 50 microns, at least about 45 microns,
at least about 40 microns, at least about 35 microns, at least
about 30 microns, at least about 25 microns, at least about 20
microns, at least about 15 microns, at least about 10 microns, at
least about 5 microns and at least about 1 micron.
Embodiment 35
[0109] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the substrate has a
thickness of not greater than about 500 microns, not greater than
about 200 microns, not greater than about 100 microns, not greater
than about 90 microns, not greater than about 80 microns, not
greater than about 75 microns, not greater than about 70 microns,
not greater than about 65 microns, not greater than about 60
microns, not greater than about 55 microns and not greater than
about 50 microns.
Embodiment 36
[0110] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the first layer
directly contacts the substrate, the first layer directly contacts
the second layer and the first layer directly contacts the
substrate and the second layer.
Embodiment 37
[0111] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the electrode further
comprises a third layer overlying the first layer and the second
layer.
Embodiment 38
[0112] The electrode, biosensor test strip, composite and method of
embodiment 37, wherein the third layer comprises Au.
Embodiment 39
[0113] The electrode, biosensor test strip, composite and method of
embodiment 37, wherein the third layer comprises Pd.
Embodiment 40
[0114] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the first and second
layers comprise epitaxial layers, wherein the first layer comprises
a growth underlayer and the second layer comprises a metallic
overlayer, wherein the metallic over layer comprises Au or Pd.
Embodiment 41
[0115] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the electrode further
comprises a layer comprising a chemical solution.
Embodiment 42
[0116] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the electrode further
comprises an enzyme, a mediator and any combination thereof.
Embodiment 43
[0117] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the (first) electrode
is reactive to glucose.
Embodiment 44
[0118] The electrode, biosensor test strip, composite and method of
any of embodiments 1, 2, 3, 4 and 5, wherein the electrode is a
working electrode.
Embodiment 45
[0119] The biosensor test strip of embodiment 4, wherein the
electrode system further comprises a counter electrode.
Embodiment 46
[0120] The method of embodiment 5, wherein the first layer is
deposited directly onto the substrate, the layer comprising the
metal is deposited directly onto a dielectric layer or both.
Embodiment 47
[0121] The method of embodiment 5, wherein the first layer is
deposited by sputtering, the second layer is deposited by
sputtering or both.
Embodiment 48
[0122] The method of embodiment 5, wherein the first layer and the
second layer are deposited simultaneously using a roll-to-roll
coater.
Embodiment 49
[0123] The method of embodiment 5, wherein the inorganic material
of the first layer has a standard deposition rate.
Embodiment 50
[0124] The method of embodiment 5, wherein the first layer is
deposited without annealing.
Embodiment 51
[0125] The method of embodiment 5, wherein the second layer is
deposited at a low pressure.
Embodiment 52
[0126] The method of embodiment 5, wherein the second layer is
deposited at a pressure of not greater than about 3 mTorr.
EXAMPLES
Example 1
[0127] Six sample electrodes S1-S6 were formed by depositing a
layer of aluminum-doped zinc oxide (AZO) from a ceramic target and
a layer of ruthenium (Ru) on a glass substrate. Sample electrodes
S1-S6 have a stack configuration of Glass/AZO/Ru. The AZO and Ru
layers were formed on the glass substrate with a batch magnetron
sputtering deposition machine, with a low power density applied on
the target. The thicknesses of the AZO and Ru layers for the
respective examples are listed in Table 1.
[0128] Comparative sample electrodes CS1-CS7 were formed for
performance comparison to the sample electrodes S1-S6. Comparative
sample electrode CS1 has a stack configuration of Glass/Ru. The
thickness of the Ru layer for the respective comparative sample CS1
is listed in Table 1. Comparative sample electrodes CS2-CS7 have a
stack configuration of Glass/Ru/AZO. The thicknesses of the AZO and
Ru layers for the respective examples are listed in Table 1.
[0129] Each sample electrode S1-S6 and comparative sample
electrodes CS1-CS7 were measured to determine the sheet resistance
of the electrode. The measurements were taken according to an
electromagnetic non-contact method using a Nagy apparatus. The
results are reported in Table 1 below.
TABLE-US-00001 TABLE 1 Sheet Resistance Ru Deposition Improvement
AZO Ru Pressure R/sq Resistivity (AZO underlayer/ Samples (nm) (nm)
(mTorr) (Ohm/sq) (.mu.Ohm cm) AZO overlayer) CS1 -- 75 1.5 2.68
20.1 -- CS2 5 5 1.5 83.0 41.5 19.8% S1 5 5 1.5 66.6 33.3 CS3 5 10
1.5 27.3 27.3 20.5% S2 5 10 1.5 21.7 21.7 CS4 5 56 1.5 3.7 20.9
14.4% S3 5 56 1.5 3.2 17.9 CS5 5 5 6 302.0 151 32.6% S4 5 5 6 203.6
101.8 CS6 5 10 6 116.0 116 46.4% S5 5 10 6 62.2 62.2 CS7 5 56 6
17.8 99.5 26.7% S6 5 56 6 13.0 72.9
[0130] The results in Table 1 confirm that for a wide range of
Ruthenium thicknesses and for two different deposition pressures,
an AZO underlayer contributes to a significant reduction of
resistivity.
Example 2
[0131] Three sample electrodes S7-S9 were formed by depositing a
layer of aluminum-doped zinc oxide (AZO) from a ceramic target and
a layer of ruthenium (Ru) on a PET substrate. Sample electrodes
S1-S6 have a stack configuration of PET/AZO/Ru. The AZO and Ru
layers were formed on the PET substrate with a batch magnetron
sputtering deposition machine, with a low power density applied on
the target. The thicknesses of the AZO and Ru layers for the
respective examples are listed in Table 2. Further, the deposition
pressure for application of each Ru layer is also listed in Table
2.
[0132] Three comparative sample electrodes CS8-CS10 were formed for
performance comparison to the sample electrodes S7-S9. Comparative
sample electrodes CS8-CS10 have a stack configuration of PET/Ru.
The thicknesses of the Ru layer for the respective comparative
sample CS8-CS10 are listed in Table 2. Further, the deposition
pressure for application of each Ru layer is also listed in Table
2.
TABLE-US-00002 TABLE 2 Sheet Resistance Ru Deposition Improvement
AZO Ru Pressure R/sq Resistivity (AZO underlayer/ Samples (nm) (nm)
(mTorr) (Ohm/sq) (.mu.Ohm cm) AZO overlayer) CS8 -- 70 1.5 2.9 20.3
20.7% S7 5 70 1.5 2.3 16.1 CS9 -- 70 2 2.7 18.9 22.2% S8 5 70 2 2.1
14.7 CS10 -- 70 6 24 168 61.3% S9 5 70 6 9.3 65.1
[0133] Table 2 confirms that when deposited on a PET substrate, for
a wide range of Ruthenium thicknesses and for three different
deposition pressures, an AZO underlayer contributes to a
significant reduction of resistivity.
Example 3
[0134] Two sample electrodes S10 and S11 were formed by depositing
a layer of aluminum-doped zinc oxide (AZO) from a ceramic target
and a layer of ruthenium (Ru) on a glass substrate. Sample
electrodes S10 and S11 have a stack configuration of Glass/AZO/Ru.
The AZO and Ru layers were formed on the PET substrate with a batch
magnetron sputtering deposition machine, with a low power density
applied on the target. The thicknesses of the AZO and Ru layers for
the respective examples are listed in Table 3.
[0135] Two comparative sample electrodes CS11 and CS12 were formed
for performance comparison to the sample electrodes S10 and S11.
Comparative sample electrodes CS11 and CS12 have a stack
configuration of Glass/Ru. The thicknesses of the Ru layer for the
respective comparative sample CS11 and CS12 are listed in Table
3.
TABLE-US-00003 TABLE 3 Ru Deposition AZO Ru Pressure Samples (nm)
(nm) (mTorr) S10 5 56 1.5 S11 5 56 1.5 CS11 -- 90 6 CS12 -- 90
6
[0136] FIG. 2a is chart comparing the X-ray diffraction plots for
sample electrode S10 and comparative sample electrode CS11. FIG. 2a
shows that addition of AZO underlayer strongly enhances intensity
of peak at 420, meaning a more crystalline ruthenium layer. The
peak at 440 almost disappears on the diffraction plot for sample
electrode S10, which includes an AZO underlayer. FIG. 2a also shows
that crystallites have been orientated in the same direction by the
addition of an AZO. In the diffraction plot for comparative sample
electrode CS11, without any underlayer, two different orientations
exist. This means that there is a higher relative disorder within
the sample electrode CS11, causing the higher resistivity.
[0137] FIG. 2b is chart comparing the X-ray diffraction plots for
sample electrode S11 and comparative sample electrode CS12. FIG. 2b
shows the main preferential orientation of crystallites is switched
when an AZO underlayer is added. The diffraction plot for sample
electrode S11 shows a peak at 440 that is reduced and the one at
420 is strongly enhanced relative to the diffraction plot for
comparative sample electrode CS12. Further, the diffraction
spectrum of sample electrode S11, with an AZO underlayer, is close
to the one of a Ru layer deposited at 1.5 mTorr. This is consistent
with the reduction of resistivity that occurs when AZO underlayer
is used in an electrode.
[0138] Note that not all of the activities described above in the
general description or the examples are required, that a portion of
a specific activity can not be required, and that one or more
further activities can be performed in addition to those described.
Still further, the order in which activities are listed is not
necessarily the order in which they are performed.
[0139] Benefits, other advantages, and solutions to problems have
been described above with regard to specific embodiments. However,
the benefits, advantages, solutions to problems, and any feature(s)
that can cause any benefit, advantage, or solution to occur or
become more pronounced are not to be construed as a critical,
required, or essential feature of any or all the claims.
[0140] The specification and illustrations of the embodiments
described herein are intended to provide a general understanding of
the structure of the various embodiments. The specification and
illustrations are not intended to serve as an exhaustive and
comprehensive description of all of the elements and features of
apparatus and systems that use the structures or methods described
herein. Separate embodiments can also be provided in combination in
a single embodiment, and conversely, various features that are, for
brevity, described in the context of a single embodiment, can also
be provided separately or in any subcombination. Further, reference
to values stated in ranges includes each and every value within
that range. Many other embodiments can be apparent to skilled
artisans only after reading this specification. Other embodiments
can be used and derived from the disclosure, such that a structural
substitution, logical substitution, or another change can be made
without departing from the scope of the disclosure. Accordingly,
the disclosure is to be regarded as illustrative rather than
restrictive.
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